[cfe-commits] [PATCH] Set region size in GRRegionVals transfer function

[Ted Kremenek]

On Nov 7, 2008, at 8:37 AM, Zhongxing Xu wrote:

>
>
> On Fri, Nov 7, 2008 at 11:40 PM, Ted Kremenek <kremenek at apple.com>  
> wrote:
>
> On Nov 7, 2008, at 12:44 AM, Zhongxing Xu wrote:
>
> From what I can tell, an out-of-bounds check has three components:
>
> (1) a location L, which is an offset within a region X
> (2) the extent of region X
> (3) some logic to determine if the location L is outside the extent  
> of region X
>
> We need to decide if we currently represent (1) for the interesting  
> cases that we are initially interested in going after.
>
> I have some difficulty to understand this sentence. I think a we  
> will just get a location MemRegionVal with a out-of-bound  
> ElementRegion, returned by getLValue(). And nobody is aware of its  
> illegality at that time.
>
> Sorry.  ;-)
>
> I meant can we represent all "locations" (using SVals) for the cases  
> that would be most interesting for array bounds checking?  At this  
> point I think the answer is no, since we don't have a location that  
> represents a "base" + "offset", where the base is a location (i.e.,  
> a MemRegion) and offset is an index off of that base.  Currently we  
> drop all pointer arithmetic operations on the floor, so we haven't  
> had to reason about such things yet.
>
> I think we have. That is an ElementRegion with a symbolic SVal as  
> its index. Because all 'base'+'offset' boils down to an array element.

That's right.  Wonderful.
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